Topic Contents

Gastrin

Test Overview

A gastrin test measures the level of the
hormone gastrin in the blood. Gastrin is produced by
cells, called G cells, in the stomach lining. When food enters the stomach, G
cells trigger the release of gastrin in the blood. As blood levels of gastrin
rise, the stomach releases acid (gastric acid) that helps break down and digest
food. When enough gastric acid has been produced by the stomach, gastrin levels
in the blood drop.

How To Prepare

Do not eat or drink anything with caffeine, such as coffee, for 12 hours before the test.

Do not
chew gum or smoke cigarettes for 4 hours before the test.

You can
drink as much water as you want up to 1 hour before the test.

Many medicines can change the results of this test.
Be sure to tell your doctor about all the nonprescription and prescription
medicines you take, especially acid-reducing medicines, such as Pepcid,
Prilosec, Rolaids, Tums, or Zantac. You may need to stop taking some medicines before this
test.

Stress can affect gastrin levels, so you may be asked to rest quietly for
30 minutes before the blood sample is drawn.

Talk to your doctor
about any concerns you have regarding the need for the test, its risks, how it
will be done, or what the results will mean. To help you understand the
importance of this test, fill out the
medical test information form(What is a PDF document?).

How It Is Done

The health professional taking a sample
of your blood will:

Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.

Clean the needle site with
alcohol.

Put the needle into the vein. More than one needle stick
may be needed.

Attach a tube to the needle to fill it with
blood.

Remove the band from your arm when enough blood is
collected.

Put a gauze pad or cotton ball over the needle site as
the needle is removed.

Put pressure on the site and then put on a
bandage.

For a secretin test, a blood sample is drawn and then the
digestive hormone secretin is injected into a vein in your arm. Additional
blood samples are drawn at the time of the injection, then every 5 minutes
until 15 minutes have passed, and then again at 30 minutes after the secretin
injection.

How It Feels

The blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or
pinch.

Risks

There is very little chance of a problem from
having a blood sample taken from a vein.

You may get a small bruise at the site. You can
lower the chance of bruising by keeping pressure on the site for several
minutes.

In rare cases, the vein may become swollen after the blood
sample is taken. This problem is called phlebitis. A warm compress can be used
several times a day to treat this.

Ongoing bleeding can be a
problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and
other blood-thinning medicines can make bleeding more likely. If you have
bleeding or clotting problems, or if you take blood-thinning medicine, tell
your doctor before your blood sample is taken.

Results

A gastrin test measures the level of the
hormone gastrin in the blood. Results are usually available in 1 to 2
days.

Normal

The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Low levels

What Affects the Test

Reasons you may not be able to
have the test or why the results may not be helpful include:

Eating before the
test.

Drinking caffeinated beverages or alcohol right before the
test.

Taking some medicines. Examples of medicines that can affect results include medicines that reduce stomach acid (such as Pepcid, Prilosec, or Zantac) and medicines or supplements that contain calcium (such as Tums or a daily vitamin). Make sure your doctor knows about all the medicines, herbs, and supplements you take.

Having had stomach ulcer
surgery or a small bowel resection. Increased gastrin levels also occur in
medical conditions such as kidney failure,
rheumatoid arthritis, and
cirrhosis.

What To Think About

The level of gastrin in the blood varies
throughout the day, but it is usually lowest in the
morning.

Gastrin test results are most useful when they are
evaluated along with medical information gathered from other examinations or
tests.

If you have normal or mildly elevated gastrin levels but
continue to have problems with peptic ulcers, further blood testing may be
done. An intravenous secretin test helps determine whether peptic ulcers are
being caused by Zollinger-Ellison syndrome. Gastrin levels generally increase
by more than 200 picograms per milliliter (pg/mL) in people who have
Zollinger-Ellison syndrome, but they rise only slightly or decrease in people
who do not have the syndrome.

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